http://hdl.handle.net/10204/919 2013-06-18T05:38:09Z 2013-06-18T05:38:09Z Shoke, L Sono, TJ Olubambi, PA http://hdl.handle.net/10204/6783 2013-06-12T21:55:29Z 2013-04-01T00:00:00Z

Title: Utilization of ISO 6892:2009 testing standard for determining tensile properties of TM380 mild steel Authors: Shoke, L; Sono, TJ; Olubambi, PA Abstract: The aim of this study was to develop an in-house tensile testing procedure that would yield accurate and reproducible parameters as input material properties into computational models for numerical simulations of the mechanical behaviour of TM380 mild steel. To achieve this objective, we reviewed the ISO 6892:2009 tensile testing standard along with reported good practice guidelines. Tensile tests were conducted on a dog-bone shaped TM380 mild steel specimen with strain gauges attached on either side, to monitor alignment and measure strain, using three different types of tensile testing machines. Parameters quantified included yield stress, ultimate tensile strength, and modulus of elasticity. The values of these parameters were found to be in agreement with the values supplied by the manufacturer's specification and showed minimal variations between laboratories. Thus it can be concluded that the tensile test procedure used resulted in accurate and reproducible results. The strain values calculated as per standard were in disagreement with those determined from extensometer and strain gauges and resulted in lower elastic modulus values. This confirms that the current testing procedures require the use of long-range strain gauges or extensometer to determine the strain. A chemical analysis was conducted to verify the specification by the manufacture. The specimen was found to be fairly homogeneous with minor sulphide inclusions. The micrographs reveal a pearlite and ferrite structure typical of mild steel, and the fractographs show a dimpled surface typical of ductile fracture, which is an attribute of mild steel. Description: Copyright: 2013 SAIMM. This is an ABSTRACT ONLY. The definitive version is published in Journal of the Southern African Institute of Mining and Metallurgy, vol. 113, pp 1-6

2013-04-01T00:00:00Z Chauke, L Möller, H Curle, UA Govender, G http://hdl.handle.net/10204/6781 2013-06-12T21:55:28Z 2012-10-01T00:00:00Z

Title: Industrial heat treatment of R-HPDC A356 automotive brake callipers [Conference paper] Authors: Chauke, L; Möller, H; Curle, UA; Govender, G Abstract: Heat treatment of rheo-high pressure die cast (R-HPDC) A356 brake callipers has produced good mechanical properties on the laboratory scale. An industrial heat treatment is required to evaluate the applicability and conformance of the R-HPDC A356 brake callipers to the automotive industry. This research studied A356 brake callipers heat treated on the industrial scale with particular emphasis on the resulting microstructure, hardness and tensile properties. The eutectic Si-particle spheroidisation after solution heat treatment was achieved and observed with optical microscopy. A hardness increase from 64 to 100 Vickers was achieved from the as-cast condition to the industrially heat treated T6 condition. The heat treatment caused no significant variation in hardness and tensile properties from brake callipers within the same batch or from different batches. The yield and ultimate strengths of the industrial heat treated brake callipers were lower compared to the laboratory scale heat treatment properties, while the ductility increased, mainly due to quenching effects. Even though the industrial heat treated A356 brake callipers resulted in yield and ultimate tensile strengths lower than those achieved on a laboratory scale, they still exceeded the minimum specifications for gravity die cast A356 brake callipers. Description: S2P 2012 12th International Conference on Semi-Solid Processing of Alloys and Composites, Cape Town South Africa, 8-11 October 2012

2012-10-01T00:00:00Z Bolokang, AS Phasha, MJ Camagu, ST Motaung, DE Bhero, S http://hdl.handle.net/10204/6773 2013-06-13T21:55:14Z 2012-03-01T00:00:00Z

Title: Effect of thermal treatment on mechanically milled cobalt powder Authors: Bolokang, AS; Phasha, MJ; Camagu, ST; Motaung, DE; Bhero, S Abstract: Stabilization of the metastable FCC phase has been achieved after 10 h milled Co powder sintering at 1400 °C. Phase identification of the Co powders was performed by the X-ray diffraction analysis, while the microstructural analyses were performed by scanning electron microscopy. Phase transformation on the metal was traced by the differential scanning calorimetry. Description: Copyright: 2012 Elsevier. This is a Pre/post print version of the work. The definitive version is published in International Journal of Refractory Metals and Hard Materials, vol. 31, pp 258-263

2012-03-01T00:00:00Z Mahamood, RM Akinlabi, ET Shukla, M Pityana, RM http://hdl.handle.net/10204/6749 2013-05-28T21:55:15Z 2012-01-01T00:00:00Z

Title: Revolutionary additive manufacturing: an overview Authors: Mahamood, RM; Akinlabi, ET; Shukla, M; Pityana, RM Abstract: Consumer demands are moving away from standardized to customized products, as such, the evolution of alternative manufacturing technique has become imperative. Additive manufacturing (AM) is a process of building components layer by layer as against the traditional methods which are subtractive in nature. Though AM offers lots of advantages over traditional manufacturing techniques, its wide application is still however at the infancy phase. Despite all the benefits derived from AM technology, there are still a lot of unresolved issues with the technology that has hindered its performances thereby limiting its application to high tolerant jobs. This paper takes a look at some important AM technologies, some problems currently facing AM technology at large and proposes some solutions to these problems. A major known drawback in AM is poor dimensional accuracy and poor surface finish, only the layer height and melt pool temperature are controlled to solve this problem in the literature. The stair-stepping effect in adaptive manufacturing is rooted in a natural phenomenon of surface tension which is the cause of the poor surface finish and in combination with other factors is responsible for the poor dimensional accuracy. An adaptive controller is proposed for removing stair-stepping effect to improve the dimensional accuracy, the surface finish and the mechanical properties of the components. Successful implementation of these proposed controllers will greatly improve the performances of AM technologies and also aids its wide application for end use products. Further research works are also suggested to improve the overall AM performances. Description: Copyright: 2012 Old City Publishing. This is an ABSTRACT ONLY. The definitive version will be published in Lasers in Engineering, pp 1-18

2012-01-01T00:00:00Z